Arctic Ocean salinity, temperature and waves

[uniquorn]

I thought this topic needed a dedicated thread as comments tend to get lost in the freezing/melting season threads. Fish Out of Water noticed a rapid increase in salinity at 300m on the Mercator Ocean model and questions were raised as to it's validity. Snips and links below

Update on Mercator 300m salinity, aug1-sep30. (every 2days, scale is not static)
http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20180801/20180930/2/4

Is this still real? And if so, any explanations?

If it was a Kelvin wave from the deep waters, this could change the whole dynamic of the arctic: lowering freezing temps, holding more heat in summer, drawing up a long chain of warmer water? and likely half hidden under the existing pack as it looks to only show around the edges!  Wondering if the 'bobbing effect' of so many smaller bergs might serves as a pump to circulate itself.

<snippage> another possibility is that the saline water is moving across the Beaufort at depth and is backing up in the direction it's coming from and merely leaking into the Beaufort gyre following the shelf bathymetry. That is it's Atl. water.

<snippage>
I think the wind shift caused a coastal Kelvin wave of shoaling of warm salty Atlantic water from depths below 300m up to the 300m level. I have forgotten who suggested it was a Kelvin wave, but I think that's correct because shifts in wind regimes can cause coastal Kelvin waves.
Extraordinary amounts of warm salty Pacific water have been flowing towards the Barrow submarine canyon, but that water hasn't had the time to reach the CAA and loops show that that water may be rotating clockwise towards the Chukchi shelf margins, not the CAA. The warm water that's sinking in the Chukchi region will likely store heat in the water layers above 300m.
<snippage>

Is it likely that long distance waves and, to some extent, tidal movements have been suppressed by thick pack ice and that, as the percentage of open water increases, we will begin to see evidence of larger scale 'bottom mixing' as well as more localised storm driven 'top mixing' of arctic waters?
As the Windy wave image shows, the damping effect of arctic ice appears to be diminishing.
Mercator 300m salinity and temperature, aug1-oct4.
Windy ecmwf waves and SST, oct4

[uniquorn]

A great bathymetry map from NOAA. It uses very different bright colours that are easily distinguishable, even in small images.
Another one with names that will be helpful (for me, at least)

[uniquorn]

We can go back further to see where it starts but salinity is already high at 300m near the alaskan coast at the beginning of august. It builds up rapidly in the Beaufort Sea, west of the CAA, near the Mclure Strait. FOoA suggests that it's too fast to be flowing around the coast so it is probably 'upwelling' from saltier water below. (I'm not sure how a kelvin wave does this yet)
There is also a salinity build up west of the Chukchi Plateau which I find easier to understand as it would appear to be incoming salty pacific water sinking as soon as it reaches deeper water.

The changes on the Mercator temperature chart are more subtle but there is a noticable increase in both higher salinity areas, especially west of the Chukchi plateau.

Interesting how much activity there is in the Fram Strait at 300m

[johnm33]

I've modified my take a little, looking at Mercators various offerings it's clear there's no temperature build up associated with the salinity increase at the base of Amundsen gulf, so I think that it's a deeper layer being forced in that direction, a combination of Atl. water penetration past Lomonosov into the Pacific/Canadian side and the tidal movements of Amundsen.
   It looks, to me, that Amundsens tidal movements are what drives the Beaufort gyre, which can rotate either way. Depending on weather conditions, at at the beggining of melt, the start up decides which way the gyre rotates in any given year. For instance I'd guess a high over the north Pacific with a low in the Pacific Arctic may force a surge of Pacific water north and that turning along the coast would force the gyre to kick start ccw.
   My ball-park maths suggest 1-200km³ of turnover in Amundsen twice a day, this year it's driving a current across the north coast of continental America, it seems at all depths. It carries any ice with a keel towards the 'blob' where it gets caught in the eddies where this coastal current turns the incoming Pacific waters west. The incoming Pacific waters are backed up and fall instead into the Chukchi abyssal plain where they appear to be met by Atl. waters.
 The easiest fraction of water to draw into the Gulf are the surface waters and since the flow has, i think, been enhanced by Atl. influx as shows in this current Beaufort hycom
 
 

[oren]

Just an ignorant question: Is there any buoy or float in that area that can verify that the anomaly is actually there? I keep wondering at Mercator's animations (and Hycom's) what the actual level of data behind them.

[uniquorn]

Thanks johnm33, shame to see that thick ice going into the Mclure Strait.
Oren, yes, thanks to Bruce Steele, but it will take me a while and a steep learning curve to verify if they match up.

There are two new ITP buoys in the Beaufort, ITP 109 and 110. They both seem to be working and sending out temperature / salinity numbers.

http://www.whoi.edu/page.do?pid=163196

ITP110 data is here ftp://ftp.whoi.edu/whoinet/itpdata/itp110grddata.zip
edit: It starts at day263, sep20 2018, so will be useful going forward.
edit2: 300m looks like a layer boundary. Hopefully ITP110 will drift into the modelled higher salinity over the next few days. (based on johnm33 hycom gif above)
edit:The Ice-Tethered Profiler data were collected and made available by the Ice-Tethered Profiler Program (Toole et al., 2011; Krishfield et al., 2008) based at the Woods Hole Oceanographic Institution (http://www.whoi.edu/itp).

[oren]

Thanks for the detective work uniquorn.

[uniquorn]

Mercator 100m salinity, aug1-oct4.
This shows more clearly the flows that johnm33 describes (not the tides). Pacific water is less saline than the Atlantic but, according to the model they are meeting at 100m west of the Chukchi plateau.
The model also shows 'leakage' over the lomonosov ridge and a steady drift of higher salinity toward Greenland, which may have contributed to recent events in the Lincoln sea. This continues along the CAA to the Mclure Strait and possibly, at reduced salinity, all the way to the Amunsen Gulf.
FOoW is probably correct that none of these flows are rapid enough to explain the salinity rise at 300m so upwelling is prime candidate.

[FishOutofWater]

Tidal effects are important but the Beaufort high is an atmospheric phenomenon not affected by ocean tides. The Beaufort high pressure area is what drives the clockwise rotation of the oceanic Beaufort gyre. When the high breaks down for weeks at a time and storms enter the region, the gyre weakens. Flow patterns change in the CAA and fresh water drains from the gyre into the CAA channels. That happened this summer.

When the high came back strong in late August and September clockwise winds caused coastal upwelling along the CAA and Alaskan continental shelves and convergence under the high pressure dome. Thus salinity increased in coastal areas where the Atlantic layer rose up in response to the wind shift and associated coastal upwelling.

Mercator also has animations of ocean currents at various layers and sea surface height anomalies. We can directly visualize what's happening at the surface by watching animations of ice movement as A-Team has shown us.

Remember that sea surface height gradients from the Pacific to the Arctic to the Labrador sea drive flows towards the Labrador sea where deep convection depresses sea surface heights.

Here's a link to Mercator's animation of currents in the 100m layer over the past 3 months or so.
http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20180701/20181004/3/3

[uniquorn]

Thanks FOoW. I struggled a bit with mercator current animations. The arrows are tricky to follow.
I did find their fixed scale salinity files though.
To my untrained eyes there isn't much supporting evidence for the 300m salinity rise at 30m so I'm posting 2018jan-oct for general background info and discussion.

Does the Mclure Strait low salinity 30m water sometimes flow up the Nares and round the top of Greenland??

tech note: this animation is created from Mercator fixed scale images but there is still some dithering on the scale (and probably within the images. This may be due to conversion from jpg to gif

[uniquorn]

I hope you don't mind if I quote your post here FOoW

The scientific literature reports that heat is not transported through the Bering strait. There is summer water in the Chukchi and Beaufort seas, but Pacific water was not found to transport heat to the Arctic ocean. That clearly is not the case this year.

Here's a link to the 30m temperature animation since July 1 this year. Heat is entering the Arctic from the Pacific through the Bering strait and it's going to be stored in the Pacific water layer below the surface. It will affect melting seasons in the years to come. It is too deep to lose it's all its heat over this winter. This is something new, beyond recent the report about heat that has been stored by sinking summer water in the Chukchi sea.

http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20180701/20181004/1/2

If we start the animation from July 1 last year, we see a push of summer water into the Arctic through the Bering strait, but nothing like what we're seeing now in terms of heat transport into the Arctic ocean.

http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20170701/20181004/1/2

[FishOutofWater]

The Coriolis effect tends to cause water to deflect to the right side of channels and passageways into and out of the Arctic ocean. Thus most water that flows out of the CAA is unlikely to flow back into the Arctic through the Nares strait. That animation does show a surge of fresh water up the Nares strait but most of that fresh water likely came from Greenland meltwater in my opinion. Obviously, with all the complex loops, small gyres and tidal effects some CAA fresh water could spin back into the Nares.

[uniquorn]

update on ITP110 profile contours. Looks like a salinity increase up to 450m....
http://www.whoi.edu/page.do?pid=163197
added location map

[uniquorn]

I'm a bit confused since ITP109 is already showing much higher salinity below ~300m
ITP109 and 110, location and T&S profile contours

[SteveMDFP]

I'm a bit confused since ITP109 is already showing much higher salinity below ~300m
ITP109 and 110, location and T&S profile contours

You're right of course.  It doesn't make sense that the profiles should look so different.
I'd hazard to guess that some malfunction started in buoy 110 fairly early on--the ?artifact? early in the 110 tracing leads me to that conclusion.

These profiles are often difficult to interpret.  What many of us might be most interested in is how the temperature and salinity profiles change year-over-year in various locations.  Damned near impossible to sort that out.

What's absolutely maddening is that relevant data to sort this out already exists.  The US has been sending nuclear subs through the arctic continuously since the 1950s.  They surely measure temperature (and probably salinity) as they go, along with depth.  But I'm quite sure the tracks of the nuclear sub movements are highly classified.  Grr.

It does seem the US military, and especially the Navy, has been taking climate change more seriously than any other branch of government.  I surmise that worrisome changes in these measurements have been noted for quite some time.

[FishOutofWater]

Remember that there is a fresh water pool more or less centered under the atmospheric Beaufort high pressure area. When buoys move from the center of that pool towards the continental shelf the salinity increases through most or all of the profile. There may be glitches in the raw buoy reports but much of what we are seeing is explained by basic facts oceanographers already know about the Beaufort gyre and regional oceanography.

Our fundamental problem causing confusion here is that physical oceanography involves complex physics and most of us aren't experts.

[uniquorn]

If it was a malfunction, wouldn't the temperature profile be similarly affected? Not if it's a sensor problem.

Remember that there is a fresh water pool more or less centered under the atmospheric Beaufort high pressure area. <snippage>

It looks like a deep pool but we should see if the sensor is ok in a few days.

Mercator Temperature 30m, jun2017-oct2018, every 7days. According to the model, heat was lost everywhere except North of Svalbard at 30m in 2017/18 freezing season. It looks like there is more heat in the Chukchi this year.

[johnm33]

Just a thought on the buoys, the deeper layers do not mix easily if a stream/current began to flow it may simply form it's own 'channel' on a deeper layer. Since I suspect the flow originates with 50%+ Pacific water falling into the Chukchi abyssal plain which rounds the Chukchi plateau before heading east that would fit. I think.
The animation at 9 above seems to be showing the circulation rounding the whole Amerasian basin.

[uniquorn]

Mercator 300m current, oct8 though it's probably easier to see in the salinity/temp animations. I'm not sure how to match the buoy locations to the mercator model.

[uniquorn]

I won't update the buoy data every day, just until things settle down a bit.
ITP110 appears to be recovering from a glitch at day265 or it had a shock event followed by a low salinity area.
ITP109 has a milder event at day275.
I suppose if you were looking for a slow velocity wave there might be something to investigate there. Perhaps it is all glitches.

"The Ice-Tethered Profiler data were collected and made available by the Ice-Tethered Profiler Program (Toole et al., 2011; Krishfield et al., 2008) based at the Woods Hole Oceanographic Institution (http://www.whoi.edu/itp)."

[johnm33]

I was thinking more of a low velocity but coherent current more direct than the model shows, and thought the eddies would be suppressed that deep, but I guess whichever way the current moves it rotates and bends. There may be no glitches, if the sensor is crossing a deep current or heading in the same direction the rate of change will vary, I'm in no position to judge if that's what's happening.

[uniquorn]

So maybe they tethered itp110 almost directly over a freshwater current heading for the Mclure Strait. A bit deep for that though, isn't it?

Looking less like a glitch today as the temperature  profile at depth is matching salinity on 110.

Can anyone recommend a temp/salinity profile contours tutorial?

[uniquorn]

Not wanting to skip around too much but since waves are in the thread title, here is oct10-19 ecmwf wave forecast from windy.
For a change of model, Hycom sea surface temperature, mar-oct9.

[uniquorn]

Back to ITP110. X marks the spot on the image below where I think ITP110 is today. An estimate based on the latest drift track above. Salinity at 300m there is modelled at ~34.5. The scales are different but ITP110 had simliar 300m salinity until recently.
If it keeps heading towards the Mclure Strait there should be a significant rise.

[uniquorn]

I looked at the [edit] last few data files and I don't think there is a problem with ITP110 (down to 300m). We'll see.  Latest measurements:
ITP110 300m salinity 34.5047 temp 0.1819C (0C at ~285m)
ITP109 300m salinity 34.4592 temp -0.1894C (0C at ~315m)

[uniquorn]

It appears that ITP107 may help....

The Ice-Tethered Profiler data were collected and made available by the Ice-Tethered Profiler Program (Toole et al., 2011; Krishfield et al., 2008) based at the Woods Hole Oceanographic Institution (http://www.whoi.edu/itp).

[Bruce Steele]

Unicorn, There are six new ITP buoys that are all working. I am interested in the depth of the surface fresh water layer at the center of the Beaufort Gyre. It may be awhile till any of the new buoys get there however. The one profiler ( 108 ) that was working for the 2018 melting season never did join the clockwise spin of the Beaufort gyre and instead made a straight line from launch to the Amundsen Gulf. It's course made me wonder if some of the Beaufort surface fresh water exited with the buoy .

[uniquorn]

Great, I'll add them to the gif tomorrow

[Sleepy]

Nice thread., thanks.
New paper here:
Arctic sea ice thickness, volume, and multiyear ice coverage: losses and coupled variability (1958–2018)
http://iopscience.iop.org/article/10.1088/1748-9326/aae3ec
Article at NASA:
With Thick Ice Gone, Arctic Sea Ice Changes More Slowly
https://www.jpl.nasa.gov/news/news.php?feature=7258

Edit; not sure if this is useful but also adding a pdf by Mikhalewsky from last year and the link to the SCICEX data.
https://www.ldeo.columbia.edu/res/pi/SCICEX/

[uniquorn]

Thanks for those sleepy. Here are the latest data from 6 active ITP's.
Thanks to Woods Hole Oceanographic Institute http://www.whoi.edu/page.do?pid=163197)
edit:@Bruce Steele. What are your rough coords for the centre of the Beaufort Gyre?

[Bruce Steele]

Uniquorn, Generally I look at the BGOS buoys as bounding the gyre. If you look at itp 109 as being the closest you can see it also has the surface fresh water closest to the surface in contrast to the other buoys currently sending data. I would think the buoys closest to the center of the gyre should have the deepest surface fresh water layer. You can check out completed missions to get past data. Itp 85 tracked fairly close to where itp 109 has tracked or itp 78 for a buoy that did a circle around the gyre.
I probably should defer to Fish Out of Water on the drivers of the current status but I wonder about the gyre spinning counterclockwise this fall and the effects of that relaxation event. Fish had this to say over on the freezing season page today

"The problem on the Bering side is the unprecedented heat flux into the Arctic. Warm, moderatly salty Pacific water has flowed into the Arctic then descended to the 30m to 100m level, below the fresh water layer caused by Siberian river influx.

There's a rapidly growing amount of heat in the Pacific water layer above the Atlantic water layer which is shoaling as freshwater is flowing out of the Arctic through the CAA and the Fram strait."

So is the shoaling of the warm Pacific water, evidenced by itp 109 ,displacing the surface water or did the surface water spin out with the relaxation of the clockwise rotation of the gyre ?

[uniquorn]

Probably a good time to post Mercator 0m salinity, jul2017-oct2018, every 4days. The model does show a slow down in rotation. Not sure about counter clockwise yet.

[uniquorn]

Posting ascat mar-oct, every 3 days just to verify surface movement in the Beaufort. (sorry, no dates on this one)
say goodbye to all that MYI

[Bruce Steele]

Uniquorn, OK there doesn't look like there was a reversal. Next question , how much evidence do we have that surface fresh water layer has thinned? Was there a relaxation of the gyre and how long would it take for a measurable portion of the surface water to excape its grip . I am hoping this years deployment of ice tethered profilers will show us some more about the surface layer questions closer to the center of the gyre.
 Thanks for the great animations.

[uniquorn]

we have a lot of acorns this year

[FishOutofWater]

It's the Atlantic water that has been rising up - shoaling, as we have noted, at the 300m level near the continental margin. The Pacific water layer can be inferred on the Beaufort side of the Arctic on Mercator by the 100m layer mapping of salinity. Unfortunately, Mercator isn't particularly useful for looking at temperature anomalies that might be related to the Pacific layer.

I'm making the conclusion on where the incoming Pacific water is going based on what I can see on Mercator & SST maps about the water flowing into the Chukchi and the recent paper that traced the increase in heat content based on tracking water that sank on the margins of the Chukchi sea in recent years. I'm assuming that same thing is happening now as happened in previous years to excess summer water heat in the Chukchi.

Summer like inflow into the Chukchi has lasted longer into fall for the past 2 years. The heat this fall is shocking, but I'm assuming that it's going to have the same fate as heat from previous summers.

[FishOutofWater]

I think that cyclonic conditions around Greenland this past year caused fresh water to flow out of the Arctic ocean at higher than normal rates. The early opening of the passages of the CAA and the strong flow of sea ice through those passages this late summer are additional evidence of a strong fresh water flux through the CAA.

Here's a paper that helps explain my reasoning and if you remember this late spring and early summer there was a highly anomalous cyclonic atmospheric circulation around Greenland.

https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-13-00389.1

Abstract

Decadal changes of the liquid freshwater content in the Arctic Ocean are studied with a suite of forward and adjoint model simulations. Adjoint sensitivities show that freshwater volume changes in the Norwegian Atlantic Current north of the Lofoten basin and a salinity maximum in the Fram Strait and in the Canadian Archipelago lead to an enhanced northward transport of freshwater. The dynamical sensitivities indicate that stronger freshwater export from the Arctic is related to an enhanced cyclonic circulation around Greenland, with an enhanced export through the Canadian Archipelago and a stronger circulation within the Fram Strait. Associated with this circulation around Greenland is a large-scale cyclonic circulation in the Arctic. Cyclonic wind stress anomalies in the Arctic Ocean as well as over the Nordic seas and parts of the subpolar Atlantic are optimal to force the freshwater transport changes.

Results from a simulation over the period 1948–2010 corroborate the result that Arctic freshwater content changes are mainly related to the strength of the circulation around Greenland. Volume transport changes are more important than salinity changes. Freshwater content changes can be explained by wind stress–driven transport variability, with larger export for cyclonic atmospheric forcing. By redistributing freshwater within the Arctic, cyclonic wind stress leads to high sea level in the periphery of the Arctic, and the stronger gradient from the Arctic to the North Atlantic enhances the export through the passages. A second mechanism is the wind-driven Sverdrup circulation, which can be described by Godfrey’s (1989) “island rule” including friction. For this, wind stress in the Arctic is not important.

[uniquorn]

It's the Atlantic water that has been rising up - shoaling, as we have noted, at the 300m level near the continental margin. <snippage>

Some evidence of large salinity increase at 300m on today's whoi ITP103 profile. Second animation shows the 6 drift tracks merged and mercator 300m salinity map.

[uniquorn]

Today's itp location and profile contours. Reminded myself that mercator model is 318m (which makes quite a difference on these charts)
Will let them drift a bit before making any comment.

[uniquorn]

Last years whoi itp's for reference. Grey background to aid identification.

[uniquorn]

The Coriolis effect tends to cause water to deflect to the right side of channels and passageways into and out of the Arctic ocean. Thus most water that flows out of the CAA is unlikely to flow back into the Arctic through the Nares strait. That animation does show a surge of fresh water up the Nares strait but most of that fresh water likely came from Greenland meltwater in my opinion. Obviously, with all the complex loops, small gyres and tidal effects some CAA fresh water could spin back into the Nares.

Example of the coriolis effect in the Nares Strait. Ice tends to flow down the west side of the strait into Baffin Bay.
amsr2-uhh, nares strait, sept-oct

[johnm33]

There are tidal surges up Nares that push a current out into the arctic briefly, usually on the Ellesmere side, so arctic water, they can be exagerated by mslp differences and surface winds. It's just a temporary phenomenon, as far as I can tell, there's a powerful negative pressure in Baffin which I think is caused to a large degree by tidal harmonics. Glimpse
 We may yet see a reversal of the gyre, both Atl. and Pac. waters would be more 'comfrotable' with a ccw movement, with so much flow through the CAA a high in Bering and a low by Amundsen may be enough to force the change. How much further would the Atl. penetrate?

[uniquorn]

Hycom salinity 0m, nov2016-oct2018. It looks like clockwise rotation is set to continue.

[uniquorn]

Copied from the freezing thread

Interesting study from MIT shows a change in the rotational speed of the Beaufort Gyre due to loss of ice in that area. This seems to affect many of the parameters associated with ice drift, salinity , AMOC etc.
Perhaps other more learned Forum members might like to discuss the repercussions .....

http://news.mit.edu/2018/arctic-ice-sets-speed-ocean-current-1017

That paper is saying what A-Team and I have been saying for some time. There are a number of papers about the increase in the fresh water content of the Beaufort gyre from 2000 - 2015. We know that the gyre has spun up with the decline of multiyear sea ice and we know why. This paper quantifies it and models it.

What A-Team and I have been saying is that there is now evidence of weakening of the gyre in response to increased storminess over the past several years. The release of fresh water from the gyre is one of the causes of the cold SST anomaly in the Greenland and Labrador seas.

[uniquorn]

Just an ignorant question: Is there any buoy or float in that area that can verify that the anomaly is actually there? I keep wondering at Mercator's animations (and Hycom's) what the actual level of data behind them.

It should be noted that the last 2 or 3days of profile contours can change significantly.

ITP103
I don't understand the datafile yet but based on the profile contour chart 312m salinity has risen from ~34.7 to 34.8. That's yellowish to orange on the mercator map. Reasonable agreement.

ITP104 and 105 appear to be stuck at the moment.

ITP107
Year   Day             dbar   temp      salinity    oxygen
2018  290.02022  312    0.1960   34.6094  265.8341
Today's reading of ~34.6 agrees well with its position on the mercator map. It also had a big dip in salinity as suggested by the model.

ITP109 (no oxygen)
2018  290.02020  312   -0.0324   34.4906
Today's reading of ~34.5 agrees well with the position on the mercator map. I'm not sure it matches up so well with the mercator contours en route.
 
ITP110
2018  290.02069  312    0.2594   34.6187  264.3407
Today's reading of ~34.6 is a bit lower than the mercator map ~34.7 but the salinity changes on route do match up quite well with the map

All in all, I think there is some validity to the mercator model based on the buoy data so far.

active whoi ITP's 103-110, drift tracks and profile contours, oct17
Drift tracks merged with mercator 312m salinity map, oct17. (edited size)

all data available from http://www.whoi.edu/page.do?pid=163197

[uniquorn]

If they gave an actual link to the paper one of us could probably pull it up. Instead, they give us their science writer's PR and no link to the source.

BINGO! Found it

Googled " Beaufort Gyre Governor " and got - http://oceans.mit.edu/JohnMarshall/wp-content/uploads/2018/02/meneghello2018governor.pdf

I am supposed to be doing my personal admin but.....

Thanks for the link. This is a model study to test the hypothesis that sea ice acts as a governor to the Beaufort gyre. Here's the introductory statement to what they did:

To  explore  the  governor  mechanism  and  test  our  theoretical  model,  we  analyze  the
response of an idealized gyre under two different limit-case scenarios:  i) an ice-driven gyre
(α=1 in equation 1, in which forcing depends purely on gradients ofτ=τi) and

 ii) an ice free, wind-driven gyre (α=0, in which forcing depends purely on gradients of τ=τa).

We conclude with a discussion of the implications of the governor for the Arctic Ocean’s
circulation and its fresh water content.

The implications of this study are quite significant. Without the sea ice governor, the Beaufort gyre will go through sudden expansions and contractions. Large pulses of fresh water will be released to the Labrador sea causing sudden disruptions of the meridional overturning circulation (MOC). This will destabilize NH winter weather patterns causing swings from warm to cold over periods that haven't yet been determined, perhaps decadal or less.

[oren]

All in all, I think there is some validity to the mercator model based on the buoy data so far.

Great analysis, thanks. I was good friends with the camera-based top-measuring O-buoys, but one look at these ITP contours and my eyes glaze over.

[uniquorn]

just deglazing mine now
This weeks ecmwf wave forecast from windy.
Bigger waves maybe not making it through to the Laptev now.

[uniquorn]

Open ocean cooling steadily. Salinity still increasing on Pacific and Atlantic sides.

Mercator 0m temperature and salinity, oct1-17.

[Cid_Yama]

Arctic ice sets speed limit for major ocean current

The Beaufort Gyre is an enormous, 600-mile-wide pool of swirling cold, fresh water in the Arctic Ocean, just north of Alaska and Canada. In the winter, this current is covered by a thick cap of ice. Each summer, as the ice melts away, the exposed gyre gathers up sea ice and river runoff, and draws it down to create a huge reservoir of frigid fresh water, equal to the volume of all the Great Lakes combined.

Scientists at MIT have now identified a key mechanism, which they call the "ice-ocean governor," that controls how fast the Beaufort Gyre spins and how much fresh water it stores. In a paper published today in Geophysical Research Letters, the researchers report that the Arctic's ice cover essentially sets a speed limit on the gyre's spin.

In the past two decades, as temperatures have risen globally, the Arctic's summer ice has progressively shrunk in size. The team has observed that, with less ice available to control the Beaufort Gyre's spin, the current has sped up in recent years, gathering up more sea ice and expanding in both volume and depth.

If global temperatures continue to climb, the researchers expect that the mechanism governing the gyre's spin will diminish. With no governor to limit its speed, the researchers say the gyre will likely transition into "a new regime" and eventually spill over, like an overflowing bathtub, releasing huge volumes of cold, fresh water into the North Atlantic, which could affect the global climate and ocean circulation.

"This changing ice cover in the Arctic is changing the system which is driving the Beaufort Gyre, and changing its stability and intensity," says Gianluca Meneghello, a research scientist in MIT's Department of Earth, Atmospheric and Planetary Sciences. "If all this fresh water is released, it will affect the circulation of the Atlantic."

Meneghello is a co-author of the paper, along with John Marshall, the Cecil and Ida Green Professor of Oceanography, Jean-Michel Campin and Edward Doddridge of MIT, and Mary-Louise Timmermans of Yale University.

A "new Arctic ocean"
 
There have been a handful of times in the recorded past when the Beaufort Gyre has spilled over, beginning with the Great Salinity Anomaly in the late 1960s, when the gyre sent a surge of cold, fresh water southward. Fresh water has the potential to dampen the ocean's overturning circulation, affecting surface temperatures and perhaps storminess and climate.

Similar events could transpire if the Arctic ice controlling the Beaufort Gyre's spin continues to recede each year.

"If this ice-ocean governor goes away, then we will end up with basically a new Arctic ocean," Marshall says.
 
"In a warming world"
 
Marshall and Meneghello note that, as Arctic temperatures have risen in the last two decades, and summertime ice has shrunk with each year, the speed of the Beaufort Gyre has increased. Its currents have become more variable and unpredictable, and are only slightly slowed by the return of ice in the winter.

"At some point, if this trend continues, the gyre can't swallow all this fresh water that it's drawing down," Marshall says. Eventually, the levee will likely break and the gyre will burst, releasing hundreds of billions of gallons of cold, fresh water into the North Atlantic.

An increasingly unstable Beaufort Gyre could also disrupt the Arctic's halocline -- the layer of ocean water underlying the gyre's cold freshwater, that insulates it from much deeper, warmer, and saltier water. If the halocline is somehow weakened by a more instable gyre, this could encourage warmer waters to rise up, further melting the Arctic ice.

"This is part of what we're seeing in a warming world," Marshall says. "We know the global mean temperatures are going up, but the Arctic tempertures are going up even more. So the Arctic is very vulnerable to climate change. And we're going to live through a period where the governor goes away, essentially."

link

The research paper